<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        // 用户输入年份
        let year = +prompt('请输入年份：')
        // 判断年份类型并弹框
        if (year % 4 === 0 && year % 100 !== 0 || year % 400 === 0) {
            alert(`您输入的${year}是闰年`)
        } else {
            alert(`您输入的${year}是平年`)
        }   
    </script>
</body>

</html>